Disc brake device for motor vehicles

ABSTRACT

A disc brake arrangement for motor vehicles is disclosed which comprises at least two brake pads (4,5) supported by a brake yoke (1), one side of said pads exhibiting a friction surface (11), which is arranged to face towards a rotatable brake disc (3). In a vehicle braking position, each brake unit is brought to an active position by means of two actuators (8,9) which act against the second side (10) of said brake unit. Thereby, each actuator exhibits an end portion (21) which is intended to transfer movement of the actuators from each respective second side of the brake pad to each respective brake pad. On the second side, each brake pad exhibits a first coupling member (27,28), arranged for each actuator. The end portions of the actuators exhibit second coupling members (37,38) for positioning of the brake pads. Both the first and the second coupling members (27,28,37,38) exhibit interacting guiding surfaces, which prevent rotation of the end portion (21) of the actuators (8,9) around an axis, transverse to the second side.

TECHNICAL FIELD

The present invention relates to a disc brake arrangement for motorvehicles, according to the preamble of claim 1.

BACKGROUND OF THE INVENTION

In the brake yoke of disc brakes, the brake pad units are normallysupported in such a way within a space, that they are prevented fromrotating together with the brake disc. When the brake pad unit has worndown and the brake disc at the same time has been reduced in thickness,it may, however, occur that the brake pad unit, when almost completelyworn out, slips out of its position and rotates with the disc. This mayimply that the braking function is completely lost or that a completelocking of the brake disc occurs. In certain vehicles, transverse pinsare provided which extend through holes, in the brake pad unit and keepsthe unit in position. This construction may, however, gradually corrodeand as time goes by imply jamming which, when bigger dimensions areconcerned such as with disc brakes for heavy vehicles, may result indifficulties during maintenance.

One problem which is associated with a commonly occurring brake systemfor heavy vehicles is that the actuators, which diplace the brake padunits between braking and released position, exhibit portions at theirends which in certain conditions, e.g. when adjusting for the gradualwear of the brake pad units, are affected by torsional forces, which maycause damage to e.g. enclosing bellows and the like.

From the U.S. Pat. No. 3,162,271, it is previously known to arrangecoupling means, between actuators and brake pad units in the form ofT-shaped grooves and correponding pins on the actuators intended tointeract with the grooves. By means of this interaction, a mutualtransfer of the relative position of the actuators and the brake padunits is ensured, for instance by means of the brake pad units beingbrought to a released position by means of the return movement of theactuators. Since the pins, however, are completely rotationallysymmetric, the end portions of the actuators will not become lockedagainst rotation by means of the brake pad units. Consequently, thisdoes not offer any solution to the above-mentioned problem.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a device by means ofwhich, on the one hand, the brake pad units are prevented fromaccompanying the movement of the brake disc and, on the other hand,prevents the end portions of the actuators from being entailed inrotational movements of the actuators when adjusting for the gradualwear of the brake pad units.

Said object is achieved by means of the device according to the presentinvention, the characterising features of which are evident from thesubsequent claim 1.

By means of the device according to the invention, the brake pad unitsare kept in position so that, on the one hand, they cannot leave theirmain position in the brake yoke when worn out and, on the other hand,end portions of the actuators are maintained in a non-rotaable positionin relation to the brake pad units.

DESCRIPTION OF THE DRAWINGS:

The invention will be described in the following in greater detail withreference to an embodiment and to the attached drawings in which:

FIG. 1 shows a brake yoke provided with the device according to thepresent invention, in a partially sectioned side view,

FIG. 2 shows two brake pad units according to the invention withassociated coupling members, while

FIG. 3 shows a side view of a brake pad unit according to the inventionwith associated coupling members.

FIG. 1 shows a brake yoke 1 of a so called floating type, which therebycreates an extremely symmetrical force action on the portion of thebrake disc 3 which protrudes into a recess 2, as indicated by dottedlines. The brake disc is in a conventional way firmly attached to awheel hub for rotation together with a vehicle wheel of a motor vehicle,for instance a heavy vehicle, such as a goods vehicle. This symmetricalforce action is achieved by means of the yoke being slidable in parallelto the axis of rotation of the brake disc 3, in a not shown,conventional manner. A brake pad unit 4, 5 is arranged on each of thetwo sides 6, 7 of the brake disc, whereby in the shown exampleactuators, more exactly two 8, 9, are arranged only on one side fordirect action against the outside 10 of one of the brake pad units. Onone side of the brake pad unit, a brake pad 11 is arranged in aconventional manner, with a frictional surface which, when in a brakingposition, is intended to be pressed against the sides of the brake discby means of the actuators 8, 9 while, when in a passive off-position, itis intended to be returned into a position in which the brake pads 11are situated a small distance from the brake disc. In itself, the yokedoes not have to be of a floating type, whereby two actuators are alsoarranged on the opposite side of the yoke, on the outside of the brakepad unit 4. In the shown example, the brake pad units 4, 5 are designedas steel plates with frictional linings on one side, but may also bedesigned as a homogenous unit of a frictional material.

The actuators 8, 9 are of a mechanical type, whereby their linear,reciprocating movement between braking position and passive position, inthe direction of the arrows 12 and 13, is achieved by means of lineardisplacement of a piston 46, which is linearly movable in a bore 47 inthe yoke. The piston 46 exhibits the shape of a sleeve into which ascrew 14 with an external thread 15 extends, interacting with aninternal thread 16. The piston in the bore 47 extends along alongitudinal axis 18 transverse and essentially perpendicular to themain plane 19 of the brake pad units and, consequently, essentiallyparallel to the axis of rotation 20 of the brake disc 3. The movement ofthe pistons 46 may be achieved in a, per se, previously known way bymeans of, for instance, a pneumatic brake system which is typical forheavy vehicles. The purpose of the rotational movement of the screws 14in the two actuators 8, 9 is to gradually adjust the position of theactuators as the brake pads and the brake disc are worn, and this mayalso be done in a previously known way.

The torsional movement of the screw 14 of the actuators, however, shouldnot be transferred to the brake pad unit 5, and therefore the actuatorsare, in a conventional way, provided with a head 21 in their end facingtowards the brake pad unit 5. The heads 21 are pivotally journalled onthe associated screw by means of a simple pivot bearing 22, which forinstance may be designed as a rotationally symmetric, for instancecylindrical, pivot 23 which intrudes into a correpondingly designedrecess in the head 21 of the actuator 8. A bellows 24, made of forinstance rubber, which is expansible in the principal direction ofmovement of the actuators and therefore does not have to receive anytorsional movements, is arranged as a dirt cover between the head andthe yoke. Therefore, the bellows may at one of its ends be relativelyfirmly attached with a circumferential surface 25 to the head 21, and atits other end be firmly attached to a groove 26 which extends around theactuator and is arranged in the yoke 1. The bellows are advantageouslydesigned with reinforcement beads at their attachment sites which,consequently, are not intended to allow any sliding movement.

The heads 21 on the actuators 8, 9 exhibit power-transferring pressuresurfaces 48 which, in the shown example, are essentially planar andintended to interact with the side of the brake pad unit 10, which alsois essentially planar and facing towards the actuators. The actuatorsare situated at a carefully adapted relative distance from the two endsof the brake pad units in order to provide a uniformly distributed powertransmission across the brake pad unit 5.

As is evident from FIG. 1 as well as FIG. 2 and FIG. 3, both brake padunits exhibit coupling and guiding means 27, in the further description,for reasons of simplicity, denoted coupling members, for relativepositioning of the brake pad units 4, 5 and of the heads 21 of theactuators 8, 9. According to the shown example, the coupling members 27,28 are designed as grooves in the sides 10 of the brake pad units 4, 5,which are situated opposite the brake linings 11. The grooves aresituated so that they extend level with the ends of the actuators, i.e.their heads 21, so that the longitudinal symmetry axis 29 of the groovescrosses the longitudinal axis 18 of the actuators essentially at 90°,i.e. their direction of action.

More exactly, the grooves 27, 28 with their one end 30 emerge at theradially inner edge portion 31 of the brake pad units and terminate attheir opposite end 32 at a distance from the radially outer edge portion33 of the brake pad units 4, 5. The grooves 27, 28 exhibit anessentially U-shaped cross-section with a bottom 34, which isessentially planar in the shown example, and two opposite edge portions35, 36, which in the shown example are essentially perpendicular to thebottom and accordingly to the side 10 of the brake pad units 4, 5, andextend mutually in parallel and at the end 32 merge into a rounded, forinstance arc-shaped, portion in the shown example. This portion may initself be designed as a planar, transverse or V-shaped edge portion.

According to the invention, the actuators 8, 9 at their ends, moreexactly in the centre of their heads 21, also exhibit coupling members37, 38 for interaction with the coupling members 27, 28 of the brake padunits for said relative positioning and guiding. In the shown example,the coupling members 37, 38 of the actuators are designed as pins. Eachpin has an attachment portion 39 which is inserted into the head 21 ofthe actuator by means of, for instance, press-fitting so that aprotuberance 40, specially designed according to the invention,protrudes from the pressure surface 48 on the actuators 8, 9.

According to the invention, the coupling members 37, 38 associated withthe actuators are not rotationally symmetric around their longitudinalaxis, which corresponds to the main axis 18 of the actuators, when theprotuberances 40 are concerned, but these are designed with twoopposing, elongate guiding surfaces 41, 42 which, in the shown example,are linear and extend parallel relative to each other and exhibit arelative distance which is adapted to the width of the grooves 27, 28,i.e. the relative space between the longitudinal edge portions 35, 36 ofthe grooves. In practice, the relative distance between the edgeportions 41, 42 is essentially of the same magnitude as the width of thegrooves and in practice somewhat below, in order to cooperate with theguiding edges of the grooves with reasonable manufacturing tolerances.The tolerances may not be so large that a relative nip action may occurby means of the pins being turned. Seen in a plane essentially parallelto the side 10 of the brake pad units 4, 5, the protuberances 40 havesuch an extension a in a direction deviating from the direction of thewidth c direction, e.g. in the longitudinal direction of the grooves 27,28, i.e. in the direction of the axis 29, such that it exceeds the widthof the grooves, i.e. a is larger than b, in this example, and as isrealized according to the above, b is larger than c. In the shownexample, the protuberances 40 are designed with rounded end portions 43,44, in the shown example with an arc-shape which is adapted to the shapeof the ends 32 of the grooves 27, 28.

As is most clearly evident from FIG. 1, the longitudinal edge portions41, 42 of the protuberances 40 extend, in the shown example,perpendicularly outwards from the pressure surface 48 and thereby alsomerge in the depth direction with the extension of the grooves 27, 28 inthe depth direction. It is also evident that the extension in depthdirection of the protuberances is in practice equal to or slightlysmaller than the depth of the grooves, whereby the front surface 45 ofthe protuberances, which in the shown example is planar, does not form apressure surface but in practice exhibits a distance to the bottom 34 ofthe grooves so that the pressure forces of the actuators are transformeddirectly from the pressure surface 48 of the head 21, directly to theside 10 of the brake pad unit 5. The extension of the protuberances 40in the depth direction, however, should be so large that theprotuberances do not leave the grooves 27, 28 during the retraction ofthe actuators to a passive position. Therefore, the extension of theprotuberances 40 in the depth direction should not be smaller than thenormal stroke of the actuators, which in practice is very small.

Thus, in the shown example, there are no actuators on the opposite sideof the brake disc 3. Nevertheless, the positioning of the brake padunits 4 is still done in an analogous way. In this case, the couplingmembers 37, 38 are arranged directly in the wall 49 of the yoke and,accordingly, are firmly and non-pivotally mounted in order to provide asafe positioning of the brake pad units 4, which in a corresponding wayare provided with the above-described guiding grooves 27, 28.

By means of the above-described arrangement with the coupling membersaccording to the present invention, a positioning of the brake pad units4, 5 consequently takes place on both sides of the brake disc 3,whereby, when actuators 8, 9 are present, a relative positioning takesplace. Consequently, the object which is solved by the coupling members27, 28, 37, 38, on both sides of the yoke, is the holding of the brakepad units 4, 5 so that they are not carried with the rotation of thebrake disc 3, in the case of an extremely worn brake disc and worn brakepads 11. This is achieved by means of the guiding surfaces 41, 42 of thepins 37, 38 being brought in contact with the guiding surfaces 35, 36 ofthe grooves 27, 28, both in braking position and in an off-position.Since the stroke of the actuators, when switching between brakingposition and off-position is so small, the retaining is maintained inspite of the insignificant extension of the pins in depth. In aconventional way, an adaptation of the position of the actuators 8, 9gradually occurs, by means of a screwing movement of the screw 14, tothe wear of the brake pads and the brake disc developed as time goes by,whereby the head 21 of the actuators is kept in close contact with theside 10 of the brake pad unit 5 all the time. The coupling members,however, do not have any active retracting function or action on thebrake pad unit 5. Neither is it possible since, when the brakingpressure is discontinued, i.e. the pressure from the pressure surfaces48 of the actuators ceases and the actuator with its small movement isretracted, it is ensured by means of the movement of the brake disc thatthe brake pads are not in contact with the brake disc and become wornout in a passive position, i.e. non-braking position.

By means of the coupling members 27, 28, 37, 38 it is in additionensured that the head 21 of the actuators 8, 9 is kept non-pivotallyattached to the brake pad 5 in all positions of the actuators. This isachieved by means of the non-circular shape of the coupling members 37,38, or more exactly by means of the protuberances 40 having anextension, in any direction deviating from the transverse direction ofthe grooves 30, 34, which exceeds the width of the grooves. Also in thiscase, the guiding surfaces 41, 42 of the protuberances 40 serve asguiding and contact surfaces, against the guiding surfaces 35, 36 of thegrooves 30, which prevent torsional tendencies, arising from frictionbetween the head 21 and screw 14. In this manner, there is nodetrimental deformation of the bellows 24, which acquire a long workinglife, whereby the risk of breakdown, because of defilement and corrosionin the actuators 8, 9, is minimized. Furthermore, by means of the designof the coupling members, the risk that the brake pad units are insertedin the wrong way, with serious damage to the brake disk as aconsequence, is eliminated.

The invention is not limited to the embodiments described above andshown in the drawings, but may be varied within the scope of thesubsequent claims. The coupling members 37 may, for instance, bedesigned in another way. It is, for instance, conceivable that theextension of the protuberance in its length direction, in itself, may beequal to the width of the grooves. For instance, the protuberances maybe square, whereby their extension in at least some direction exceedsthe width of the groove, whereby a torsional locking is brought about.

I claim:
 1. A disc brake arrangement for motor vehicles, comprising atleast two brake pad units supported by a brake yoke, one side of eachsaid at least two brake pad units comprising a frictional surface, whichis arranged to face a rotatable brake disc and the other side of said atleast two brake pad units which is arranged to face an actuator,whereby, when in a position for braking the vehicle, each brake pad unitis arranged to be brought into an active position by means of at leasttwo actuators acting against said other side of each said at least twobrake pad units and to be allowed to be returned to a retracted, passiveposition, whereby each actuator comprises an end portion which isintended to transfer to each said at least two brake pad units movementof said at least two actuators towards and from said other side of saidat least two brake pad units, which on said other side of said at leasttwo brake pad units comprises a first coupling means arranged for eachactuator, whereby each actuator end portion comprises second couplingmeans arranged for positioning of said at least two brake pad units,said adjustment device exhibits a screw rotatable in each actuator, saidscrew in its end facing the brake pad unit, a pivot bearing, supportingsaid end portion of the acutators, whereby a protective bellows may bemounted between said end portion and the brake yoke, both said first andsecond coupling means comprises interacting guiding surfaces, which arearranged to prevent rotation of each end portion of the actuators aboutan axis, transverse to said other side of said at least two brake padunits.
 2. The device according to claim 1, wherein said first couplingmeans is comprised of grooves with an essentially U-shaped cross-sectionand that said second coupling means is comprised of protuberances whichare arranged to extend into the grooves and comprise, as seen in a planeessentially parallel to the side of the brake pad unit, a dimension (c)which, in the transverse direction of the grooves, is somewhat smallerthan the transverse dimension of the grooves (b), and which, in adirection deviating from the transverse direction, exceeds thetransverse dimension of the grooves.
 3. The device according to claim 2,wherein the grooves extend in parallel and that each of them comprisestwo parallel edge portions which form said interacting guiding surfacesof said first coupling means.
 4. The device according to claim 3,wherein said edge portions extend from the bottom of the grooves with anessentially planar surface perpendicular to the side of the brake padunit.
 5. The device according to claim 4, wherein the grooves comprisean end which emerges at one edge portion of the brake pad unit, and anopposite end (32) which is situated at a distance from the opposite edgeportion (33) of the brake pad unit.
 6. The device according to claim 1,wherein said protuberances are arranged on said end portion of at leasttwo actuators, protruding from a pressure surface to a height which isequal to or smaller than the depth of said groove.